Urban Wood. Why Knot?
All trees have a life cycle, so we are making every effort to save the trees we can from ending up in landfills. When city trees need to be removed, we preserve their natural beauty and also limit carbon emissions by salvaging trees lost during storms, disease, or normal senescence and recycling this wood into useable raw lumber.
Our urban wood offers a story unlike any other as they have been salvaged from our city streets… a true Street Tree Revival.
Join STR’s very own John and Danny Mahoney as they walk you through our process. 25 years ago, West Coast Arborists, Inc. (WCA) started an urban wood recycling program in collaboration with the California Department of Forestry and Fire Protection (CDF). WCA is a tree maintenance and management provider serving cities, counties, and school districts. Since a number of trees living within our city streets and parks eventually decline and require removal, it became imperative to identify ways to salvage what we could.
Introduction to Danny
Danny is my cousin! We are both sons of the owners of West Coast Arborists (WCA). Three years ago, Danny started working at the woodshop at Street Tree Revival, making tables, benches, coat racks, stools, and more out of urban wood. He has a camphor table in his house as well as a rosewood cabinet. He built his uncle a desk out of six or seven species of wood, like oak, elm, sycamore, poplar, and more.
25 years ago, WCA got a sawmill. Over time, the popularity of the sawmill grew a little until four or five years ago when we took it much more seriously and began running the mills every day.
Street Tree Revival: Urban Wood Recycling Program
Why urban wood? We have these beautiful heritage trees that provide a ton of resources and can give a new life if we allow ourselves to build something new out of them. We also once had this hundreds of years old tree that we got to witness scientists cut through and examine it, estimating it as one of the oldest in the known universe. They found bullets inside it, which was crazy. Abraham Lincoln could have stood under it. If you put it in a chipper and let it mulch up, that’s not honoring its whole story.
Another reason to use urban wood is because California is blessed with a diverse array of species of trees. San Diego has over 900 species of trees for example. The West Coast is typically a soft wood market, but there are so many exotic trees like eucalyptus globulus from Australia, Tasmanian blackwood from Tasmania, carob from Southeast Asia, eucalyptus camaldulensis, and the ficus from India. Who knew North Indian rosewood would be growing on the streets of California, Arizona, and Nevada? It is kind of invasive but look at the beautiful wood that has been going in the trash all these years.
Did you know?
From one log alone, you can get 3,500 board feet, which could be enough to floor an entire house. There are so many resources that aren’t being tapped into or not being tapped into well enough. People need to realize that what they have in their front yard is valuable beyond when it’s still standing.
124 million tons of CO2e could be sequestered nationally from urban hardwood over the next 30 years. “Could be” is key. We currently don’t have the best management practices to harvest that wood and turn it into useable lumber; it’s more beneficial for cities and contractors not to use the wood. Urban trees in the U.S. hold about 774 million tons of carbon. Look how much is stored in our urban forest right now. The more trees we plant, the bigger the waste stream will eventually be. This means we need to think about what happens to trees in their next stage of life.
50% of above-ground is suitable for solid hardwood products. We’re currently making benches from logs that can only be 20 inches wide, so we’re not just talking about the big ones. Small ones work, too.
Also, urban lumber is valued greater than forest grade because of history, unusual figure, and personal meaning. Just like how Abraham Lincoln stood under this oak tree. When we chop a tree like that down, you can turn it into something else like a table or a mantelpiece to keep the tree alive for even longer.
A board foot is a 12-inch by 12-inch by 1-inch piece of lumber. For each board foot of wood, there is 4.7 pounds of carbon. We have at least 8,000 board feet in our showroom, which equates to over 37,000 pounds of CO2 stored! Each kiln load is 3,000-4,000 board feet, which is 14,000-18,000 pounds of stored carbon. By turning this wood into lumber, it keeps the carbon from going back into the atmosphere.
STR is located all over the state, collecting trees from Northern California and milling them up there and drying them down here in Southern California or vice versa. We also do work in Arizona and Nevada, just like WCA. It takes a team to get this profound amount of wood (300 tons of green waste a day) through our systems.
We have a six-step process:
First, we remove damaged, dead, or hazardous trees from local cities.
Our goal is to replant two trees for every tree that we remove to maintain a healthy urban forest, which we do through a CalFire grant we’ve had for the past five years.
We track these logs by tagging quality logs in the field with weatherproof tags that have removal date and city information. This allows us to share tree history and track material from tree to lumber, especially if there aren’t any leaves or branches on the tree that are typically used for identification purposes.
We then repurpose the logs through sorting by species and size, trimming the logs to specific lengths, scaling the logs to track board footage entering the system, and sealing the logs with wax to prevent their drying out. Some logs are then painted for easy species identification.
We use several different mills, such as the WM1000 up in Stockton, an LT70 in Ontario, an LT40 in Stockton, and a Lucas in Ontario. These tools help it break it down into various stages.
As the wood dries, it takes an inch per year to dry, meaning for example, three-inch piece of wood per year takes three years. To dry the wood, we have a vacuum kiln, a DH kiln, and good old mother nature’s outside wind. One way we do this is stickering the wood, which means we put sticks of wood every 12 inches to create even air flow so that the water evaporates over the top. We also dead stack the wood and put it int the vacuum kiln. Deadstacking is when you don’t use stickers so that the wood loses no moisture, wrap it in plastic, and put it in the vacuum kiln. Water boils at a lower temperature so you don’t need to heat the wood up that high; the water inside the wood turns to steam, and you can dry the wood in two weeks. It seriously speeds up the process.
- One thing about drying wood in general is that most experts are drying one to five species at a time, not 45 types like we are. The vacuum kiln allows us to dry several species of wood at one time super quickly.
- We had a lot of trouble with certain species like black walnut, which typically still has pockets of moisture after it is run through the kiln. We let them air dry slowly first, like dry-aged perfection, like a fine wine, before putting them in the kiln to help try to control the humidity. Much more successful.
We have a WCA grant team, and their goals are to increase carbon sequestration by planting trees and assisting customers in meeting grant requirements.
Our saw log ID tag includes the foreman driver, the removal date, the truck number, the city of origin, the tree address, the tree species, and any additional comments. Maybe someone who lived on that street wants to be contacted to turn the wood into something amazing once it’s ready.
The Future of Urban Wood
Let’s talk about urban wood on a national scale. It’s unique to North America right now to look at urban wood waste. 44 billion board feet could be harvested in North America alone; if you stretch it out to the whole world, it’s big numbers. 30% of the hardwood lumber market could be supplemented by dying trees in urban forests.
We’re part of the Urban Wood Network West, which helps tie urban wood groups together and build standards for the community. If anyone is looking for logs, we have a curated section of logs that we want to get into the hands of makers for higher-end utilization.
When we did this presentation a year ago, we were going around to different cities to get them to understand why they should have best management practices written into their city policies around urban lumber. The goals of an urban wood utilization policy were to divert wood byproducts away from landfills and bolster a Climate Action Plan as a carbon securing measure. These would be accomplished by creating a tree removal salvaging plan, a desirable species replacement plan, and using urban wood for new construction.
Lack of a plan
One of the problems we run into, like in the city of Pomona, they had a big walnut removed. No one knows what they want out of the tree. Maybe a year or two goes by, and they ask if it’s ready without a plan. We try to process everything and make it available again even if they don’t know if they’re interested. But the city should be thinking about what happens to the wood after it comes down. If more people are prepared to turn the wood into another product, we can sequester hundreds of millions of pounds of carbon. Cities should think about that before they plant new trees.
There are lots of usable urban wood species, all of which we have catalogued over the past 25 years. While this does change all the time, we have nailed it down to the best and most popular.
Running down the list:
- blue gum ewe
- Carolina cherry
- Chinese elm
- coast live oak
- cork oak
- deodar cedar
- honey locust
- incense cedar
- iron bark ewe
- Indian rosewood,
- jacaranda- the inside has some shimmer shammer, some chatoyance. As you move it, it changes the color of the light. The first tree Danny ever planted was a jacaranda tree!
- pear and so many more.
- Danny’s top five trees:
- Magnolia – he’s been cutting a lot recently, and they’re beautiful
- Sequoia giganteum
- Lemon scented gum
- Tipuana tipu
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